1. Field of the Invention
This invention relates to an insulated magnet wire for use in a layer wound distribution transformer coil, and more specifically to a new and improved magnet wire having differential build insulation.
2. Description of the Prior Art
In many conventional windings, such as transformer windings, a wire winding for a high voltage section typically uses rectangular wire which has an enamel or polymer insulation on it for turn-to-turn insulation and utilizes paper or other layers of sheet material insulation between layers of turns of the coil to provide adequate insulation between the helically wound layers of insulated wire. The layer insulation is generally constructed from sheet material which is a uniform thickness in a width slightly greater than the width of the wire layers. It is wound into the coil as the coil is wound. After each layer the wire has been helically wound onto the coil, one or more turns of the full width layer insulation is wound onto the layer after which the next layer of wire is wound onto the coil. This process repeats through the entire coil. With conventionally wound coils, the layer insulation between layers must be thick enough to withstand the highest voltage difference between the layers. Since the windings are continuous and helically wound, the voltage between the layers varies along the coil axis or width, with the greatest voltage difference occurring between layers occurring between the starting end of a lower layer and the finish end of the layer above it. There is almost no voltage difference between the two layers on the opposite sides of the coil. The thickness of the full width layer insulation must be such that it provides the necessary dielectric strength on the start finish/side where the voltage difference between the layers is the highest. Over the remainder of the layer, the layer insulation is thicker than required.
One method of eliminating the need for the additional layer of sheet insulation between adjacent layers of the coil is disclosed in the aforesaid related applications Ser. No. 905,424 and Ser. No. 907,657,now abandoned the disclosures of which are incorporated herein by this reference thereto. In those applications the method of manufacturing the variably insulated helically wound electrical transformer coil involved integrating the insulating of the conductor into the winding process and requires a complex winding machine. The additional insulation was added to the wire in those areas of the coil where the additional dielectric strength was needed. Thereafter during the winding of the cured insulated wire into the coil of predetermined shape, the portions of the wire having additional insulation were located in the areas of the coil where the greatest dielectric strength is needed. While this method is satisfactory, it requires a complex winding machine and does prevent a supply coil of the insulated wire being prepared in advance for subsequent use in winding coils for any transformer of different sizes
It would be desirable to provide an insulated magnet wire for use in a layer wound distribution transformer coil wherein the rectangular conductor is provided with an insulation that is thicker on the top and bottom surfaces of the conductor than on the sides so that the need for additional insulation between the layers of the winding is eliminated and the same insulated magnet wire can be used in layer wound distribution transformer coils of different sizes and wound with a conventional winding machine.
The present invention relates to an insulated magnet wire for use in a layer wound distribution transformer coil which eliminates the need for a separate layer of insulation between the layers of the coil. An insulated magnet wire in accordance with the present invention includes a rectangular conductor having an insulation coating on the top and bottom and both sides of the conductor. The coating on the top and bottom of the conductor is thicker than the coating on sides of the conductor so that when the insulated conductor is wound in layers in the distribution coil, the thickness of insulation between adjacent layers in the transformer coil is greater than the insulation between adjacent turns in the coil.
Further in accordance with the invention there is provided a layer wound distribution transformer coil having multiple coil layers. Each coil layer includes multiple turns of wire, the wire having a rectangular conductor having an insulation coating on the top and bottom and both sides of the conductor. The coating on the top and bottom of the conductor is thicker than the coating on the sides of the conductor so that when the insulated conductor is wound in layers in the distribution transformer coil, the thickness of insulation between adjacent layers in the transformer coil is greater than the insulation between adjacent turns in the coil.